The present invention relates to an antenna module suitably used to electronic instruments performing wireless communications such as mobile communications or personal computers.
There have recently been more portable terminals mounted with antenna modules provided for performing wireless data communications to other electronic instruments in addition to whip antennas or built-in antennas provided for voice communication.
Besides, there have also been increased portable mobile electronic instruments such as notebook personal computers, using wireless LAN for performing wireless data communications; therefore, many of the electronic instruments have the antenna modules therein.
Further, in the recent portable telephones or notebook personal computers, miniaturization and low consumption of electric power are indispensable requirements, and an antenna device has been demanded to reduce its dimension. In addition, with increase of transmitting capacity, a broadband antenna has been required. A multi carrier system such as OFDM (Orthogonal Frequency Division Multiplexing) has more been required the broadband antenna.
Herein, for realizing the broadband and increasing the load capacity of the antenna, studies have been made on the antenna module added with an additional conductor at a lead end of the antenna (see, for example, Japanese Patent Publication No. 2002-124812 or No. 10-247806/(1998). FIG. 18 is a perspective view of the antenna module according the conventional art, and shows that the additional conductor is added to the lead end of the antenna element.
Numeral 100 designates the antenna module, 101 designates a meander antenna, 102 is an feeding portion, and 103 is an additional conductor. The meander antenna 101 is formed by a substrate pattern. The additional conductor 103 is provided at the lead end of the meander antenna 101, and this lead end is open ended. A signal current is applied from the feeding portion 102, and the applied signal is radiated in accordance with a resonance frequency of the meander antenna 101. Similarly, the signal is received. Then, the additional conductor 103 works as the load capacity, load impedance seen from the feeding portion 102 is increased, a peak of frequency curve is moderated, and the frequency band is broadened.
However, when providing the additional conductor at the lead end of the pattern antenna as the meander antenna, there has been a problem that the antenna module is large scaled, because the pattern antenna itself requires a large area.
In particular, for further advancing the broadband, the load capacity at the lead end of the antenna must be made large sized, but if being too large sized, the area at the lead end of the antenna becomes accordingly large sized, so that a problem occurs that the antenna module and the electronic instrument incorporating the antenna module are very much oversized. Further, being too large sized, a balance cannot be kept with an effect of making broadband, and efficiency is not sufficiently brought about in comparison with the large scale.